FERROELECTRIC MEMORY DEVICE

PROBLEM TO BE SOLVED: To increase the memory capacity of a ferroelectric memory device without changing the number of memory cells, by providing the device with a control circuit, which executes a writing operation of information of at least 3 values or above. SOLUTION: The control circuit 106 for writing arbitrarily controls and writes a domain polarization direction by the size of a domain inversion potential. Namely, the first writing is executed by impressing the output of a BL driving circuit 101 in order of a power-supply voltage and grounding potential in a positive direction and causing polarization in the first direction with respect to the entire domain. The second writing is executed by impressing the output of the BL driving circuit 102 in order of the power-supply voltage and grounding potential and the output of a CP driving circuit 102 in order of the voltage lower than the power-supply voltage and the grounding potential in positive, break, negative and break directions, thereby polarizing the domains of the large inversion potential to a first direction and the domains of the small inversion potential to a second direction. Further, the third writing is executed by impressing the same voltages in the negative direction and polarizing all the domains in the second direction. The fourth writing is executed by impressing the same voltages as the voltages of the second writing backward and making the domain polarization directions the same as the polarization directions of the second writing.